With the increasing development of the wireless network technology in recent years, the Wireless Local Area Network (WLAN) technology which can provide wireless connection services of the local area network attracts more and more attention from the industry. The wireless local area network has advantages of low cost, flexible networking and high rate and so on, it is widely applied in different fields such as enterprise and education and so on, and it is used by the telecom service operators for providing common wireless access services in “hotspot” areas.
The WLAN system follows a series of technical standards such as the 802.11 a/b/g/n defined by the Institute of Electrical and Electronic Engineers (IEEE) 802.11 working group. In the specification 802.11, a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism is used in the media access control protocol, to make a plurality of clients share a wireless channel. In accordance with the CSMA/CA mechanism, before sending data, one wireless device will detect an idle state of the channel, if it is discovered that related other devices are transmitting data, the wireless device does not send the data, and randomly rolls back for a period of time until the channel is idle, and if the channel is still idle at this point, it sends the data. Even though the implementation is simple, the flexibility is high and the occurrence of collision can be avoided to a certain extent in such channel competition way, the following disadvantages still exist:
1. The “Hidden terminal” problem cannot be effectively solved, that is, when two terminals cannot mutually sense a signal of the opposite party, if one of the terminals sends data, the other terminal will mistakenly think that the current channel is idle for the signal of the terminal cannot be sensed, thus it also sends the data, which causes the wireless signal collision and data retransmission. Though the 802.11 protocol proposes the request to send/clear to send (RTS/CTS) exchange protocol to solve the problem, it can only solve the hiding of the sending terminal, but cannot solve the hiding of the receiving terminal (that is, an error still exists in receiving when the terminal is hidden) and a case of collision of the RTS/CTS information package itself, and the network overhead is increased.
2. The channel utilization rate is low. After one device occupies the channel, other devices can only be in a waiting state, even though they are within a coverage scope of the device and outside a coverage scope of the receiving node, no influence will be caused on communications of the device (“exposed terminal”).
3. The network capacity is limited by the number of devices. When the number of the devices is larger and the distribution is denser, the wireless interferences between the devices are more serious, thus the network cannot accommodate excessive users, and the networking scale is limited.
In conclusion, the network utilization rate is low in the related scheduling modes.